Battery Pack Mass Estimation

Battery pack mass estimation is a key parameter required early in the conceptual design. There are a number of key reasons for estimating the mass, one of the main ones being the significant percentage it is of the overall mass of the complete system.

One option is to list all of the components and assign a mass to each. This is the ultimate method and the battery parts list is a good starting point to ensure you have every part counted.

However, early on we don’t have a detailed design from which we can estimate the mass. We can however use existing benchmark data. The following plot is the mass of everything bar the cells versus total energy.

pack total - cell mass

This can be easily turned into a simple pack mass estimation. Lots of warnings here as you can see this data has a wide spread.

The calculator uses the equation of this straight line to estimate the mass of everything other than the cells.

Step 1: estimate the total pack energy

Total energy [kWh] = S x P x Cell Nominal Voltage [V] x Cell Nominal Capacity [Ah]

Step 2: estimate the mass of everything else in the pack

Everything else [kg] = Pack mass [kg] – Cell mass [kg] = 2.052 x Total Energy [kWh] + 26.011

Step 3: add the cell mass to the everything else mass to get a total mass.

Total pack mass [kg] = Everything else [kg] + S x P x Cell mass [kg]

S and P are the number of cells in series and parallel.

Note: this is an estimate based on this being a high voltage automotive pack. The results should only be used as a rough first order indication.

Updates:

  • Tooltip added for Cells in Series: 400V packs 92s to 108s (up to 120s for LFP), 800V packs 170s to 216s
  • Tooltip for Cell nominal voltage: 3.6V to 3.7V for NMC and NCA, 3.2V for LFP

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